Polishing.

Introduce common exclusion rules for constructors.

See: #2744
Original pull request: #2746

Author: mp911de

src/main/java/org/springframework/data/util/Predicates.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.util;
 
+import java.lang.reflect.Constructor;
 import java.lang.reflect.Member;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
@@ -30,22 +31,24 @@
  */
 public interface Predicates {
 
-	public static final Predicate<Member> IS_ENUM_MEMBER = member -> member.getDeclaringClass().isEnum();
-	public static final Predicate<Member> IS_HIBERNATE_MEMBER = member -> member.getName().startsWith("$$_hibernate"); // this
+	Predicate<Member> IS_ENUM_MEMBER = member -> member.getDeclaringClass().isEnum();
+	Predicate<Member> IS_HIBERNATE_MEMBER = member -> member.getName().startsWith("$$_hibernate"); // this
 	// should
 	// go
 	// into
 	// JPA
-	public static final Predicate<Member> IS_OBJECT_MEMBER = member -> Object.class.equals(member.getDeclaringClass());
-	public static final Predicate<Member> IS_JAVA = member -> member.getDeclaringClass().getPackageName().startsWith("java.");
-	public static final Predicate<Member> IS_NATIVE = member -> Modifier.isNative(member.getModifiers());
-	public static final Predicate<Member> IS_PRIVATE = member -> Modifier.isPrivate(member.getModifiers());
-	public static final Predicate<Member> IS_PROTECTED = member -> Modifier.isProtected(member.getModifiers());
-	public static final Predicate<Member> IS_PUBLIC = member -> Modifier.isPublic(member.getModifiers());
-	public static final Predicate<Member> IS_SYNTHETIC = Member::isSynthetic;
-	public static final Predicate<Member> IS_STATIC = member -> Modifier.isStatic(member.getModifiers());
+	Predicate<Member> IS_OBJECT_MEMBER = member -> Object.class.equals(member.getDeclaringClass());
+	Predicate<Member> IS_JAVA = member -> member.getDeclaringClass().getPackageName().startsWith("java.");
+	Predicate<Member> IS_NATIVE = member -> Modifier.isNative(member.getModifiers());
+	Predicate<Member> IS_PRIVATE = member -> Modifier.isPrivate(member.getModifiers());
+	Predicate<Member> IS_PROTECTED = member -> Modifier.isProtected(member.getModifiers());
+	Predicate<Member> IS_PUBLIC = member -> Modifier.isPublic(member.getModifiers());
+	Predicate<Member> IS_SYNTHETIC = Member::isSynthetic;
 
-	public static final Predicate<Method> IS_BRIDGE_METHOD = Method::isBridge;
+	Predicate<Class<?>> IS_KOTLIN = KotlinReflectionUtils::isSupportedKotlinClass;
+	Predicate<Member> IS_STATIC = member -> Modifier.isStatic(member.getModifiers());
+
+	Predicate<Method> IS_BRIDGE_METHOD = Method::isBridge;
 
 	/**
 	 * A {@link Predicate} that yields always {@code true}.
@@ -75,4 +78,29 @@ static <T> Predicate<T> negate(Predicate<T> predicate) {
 		Assert.notNull(predicate, "Predicate must not be null");
 		return predicate.negate();
 	}
+
+	/**
+	 * Whether to consider a {@link Constructor}. We generally exclude synthetic constructors for non-Kotlin classes.
+	 *
+	 * @param candidate
+	 * @return
+	 */
+	static boolean isIncluded(Constructor<?> candidate) {
+		return !isExcluded(candidate);
+	}
+
+	/**
+	 * Whether to not consider a {@link Constructor}. We generally exclude synthetic constructors for non-Kotlin classes.
+	 *
+	 * @param candidate
+	 * @return
+	 */
+	static boolean isExcluded(Constructor<?> candidate) {
+
+		if (IS_KOTLIN.test(candidate.getDeclaringClass())) {
+			return false;
+		}
+
+		return IS_SYNTHETIC.test(candidate);
+	}
 }

src/main/java/org/springframework/data/util/TypeCollector.java

@@ -20,16 +20,7 @@
 import java.lang.reflect.Member;
 import java.lang.reflect.Method;
 import java.lang.reflect.Type;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.LinkedHashMap;
-import java.util.LinkedHashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
+import java.util.*;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 
@@ -40,9 +31,15 @@
 import org.springframework.util.ReflectionUtils;
 
 /**
+ * Collector to inspect domain types and discover the type graph that is relevant for Spring Data operations.
+ * <p>
+ * Type inspection walks through all class members (fields, methods, constructors) and introspects those for additional
+ * types that are part of the domain model.
+ *
  * @author Christoph Strobl
  * @author Sebastien Deleuze
  * @author John Blum
+ * @since 3.0
  */
 public class TypeCollector {
 
@@ -122,13 +119,16 @@ private void processType(ResolvableType type, InspectionCache cache, Consumer<Re
 	}
 
 	Set<Type> visitConstructorsOfType(ResolvableType type) {
+
 		if (!typeFilter.test(type.toClass())) {
 			return Collections.emptySet();
 		}
+
 		Set<Type> discoveredTypes = new LinkedHashSet<>();
+
 		for (Constructor<?> constructor : type.toClass().getDeclaredConstructors()) {
 
-			if (constructor.isSynthetic()) {
+			if (Predicates.isExcluded(constructor)) {
 				continue;
 			}
 			for (Class<?> signatureType : TypeUtils.resolveTypesInSignature(type.toClass(), constructor)) {
@@ -137,10 +137,12 @@ Set<Type> visitConstructorsOfType(ResolvableType type) {
 				}
 			}
 		}
+
 		return new HashSet<>(discoveredTypes);
 	}
 
 	Set<Type> visitMethodsOfType(ResolvableType type) {
+
 		if (!typeFilter.test(type.toClass())) {
 			return Collections.emptySet();
 		}
@@ -160,11 +162,14 @@ Set<Type> visitMethodsOfType(ResolvableType type) {
 		} catch (Exception cause) {
 			logger.warn(cause);
 		}
+
 		return new HashSet<>(discoveredTypes);
 	}
 
 	Set<Type> visitFieldsOfType(ResolvableType type) {
+
 		Set<Type> discoveredTypes = new LinkedHashSet<>();
+
 		ReflectionUtils.doWithLocalFields(type.toClass(), field -> {
 			if (!fieldFilter.test(field)) {
 				return;
@@ -175,6 +180,7 @@ Set<Type> visitFieldsOfType(ResolvableType type) {
 				}
 			}
 		});
+
 		return discoveredTypes;
 	}